Adolescent Health and Development in Context Abstract We propose an unprecedented data collection effort emphasizing the impact of spatial and social exposures on risk behavior, victimization, and mental/physical health for a large sample of youth (N=5,200) and their caregivers in Franklin County, Ohio. The proposed study has three overarching aims: (1) examine the influence of key structural and social process characteristics of multiple social contexts on youth developmental outcomes (risk behavior, victimization, and mental/physical health); (2) examine situational effects on youth developmental outcomes in real time; and (3) examine the extent to which youth's communities-i.e., the networks of actors and settings in which adolescents are embedded through routine exposure-influence their health and developmental outcomes. This project offers three significant advances over prior contextual studies of youth development. First, we will collect data on a comprehensive array of developmentally relevant settings including family/household, residential, school, social network, and other formal and informal activity space contexts (e.g., churches, recreation centers, businesses, and hang out locations). This multi-contextual emphasis will enable us to examine the influence of a wide range of contextual exposures on significant aspects of youth well-being. Second, we will use Ecological Momentary Assessment to collect real-time data on behavioral settings, including peer presence, adult supervision, the level of structure characterizing activities, and behavioral/health outcomes. These space-time situated network data will offer empirical linkages between the social network and spatial contexts of youth development enabling analyses of situational influences on setting outcomes. Third, we will collect geo-coded data on the spatial and organizational settings of youth activities to identify overlapping activity locations among sampled youth (e.g., subjects who spend time at the same school, church, park, etc.). This information will be used to construct actor-setting affiliation networks among youth and activity locations, capturing heretofore unmeasured community structure. Characteristics of the communities in which adolescents are embedded may have important implications for well-being, above and beyond those contexts typically measured in prior research. Our analytic approach will combine spatial and multilevel spatial statistical models to explore key hypotheses. Findings from the study have the potential to illuminate critical pathways through which contextual factors influence adolescent well-being.